The invention also relates to a method for manufacturing a section of an aircraft fuselage including a self-stiffened skin produced by means of the above method.
The invention also relates to such a fuselage section, and also to an aircraft which including the same, such as an airplane.
In the present description the term “section” may designate any type of aircraft section, including a nose cone or tail cone.
Aircraft fuselages must be able to withstand the loads caused by pressurization and the loads transmitted by the engines.
To this end, the fuselages habitually include circumferential frames, also called “orbital frames”, together with an aerodynamic skin, sometimes called a “self-stiffened skin”, attached to these circumferential frames and fitted with longitudinal stiffeners, which are attached to an inner face of the skin, and which are generally called “stringers”.
Stringers may have sections of varied types, for example T-shaped. I-shaped or Omega-shaped sections. In certain known configurations, these circumferential frames have a base plate which is attached directly to the inner face of the self-stiffened skin, in which case the frames have notches where the stringers are to pass. In other known configurations the stringers are interposed between the circumferential frames and the self-stiffened skin (the frames thus pass above the stringers), and angle pieces, commonly called “clips”, are positioned between the stringers, and connect the circumferential frames to the self-stiffened skin.
An aircraft fuselage is generally formed from several sections attached end-to-end in the longitudinal direction of the aircraft. In each section the self-stiffened skin may be formed of several panels installed end-to-end circumferentially, or be formed of several half-shells assembled with one another. The self-stiffened skin may alternatively be made from a single piece. This latter configuration, commonly called a “full barrel” configuration, notably has the advantage that it avoids the presence of junctions extending longitudinally within this self-stiffened skin.
In the case of self-stiffened composite material skins, strengthening fibers impregnated with curable resin are draped over an assembly of pre-cured composite material stringers which have been positioned beforehand in their final configuration, in order to allow co-curing of the assembly constituted in this manner.
The positioning of the stringers requires sophisticated equipment, and is generally complex to implement, in particular when a monobloc self-stiffened skin is manufactured.
US patent application US 2009/0044914 A1 describes a method for manufacturing a monobloc self-stiffened skin of cylindrical shape fitted with Omega-section stringers. This method consists in preparing a mandrel, also having the shape of a cylinder, having longitudinal grooves with a complementary shape to that of the stringers. The pre-cured composite material stringers are positioned in the grooves of the mandrel such that the base plates of the stringers are flush with the cylindrical outer surface of the mandrel, and cores are positioned within the stringers to maintain their shape, after which strips of prepreg are draped on the outer surface of the mandrel, and therefore also on the base plates of the stringers, and the assembly is co-cured so as to obtain the monobloc self-stiffened skin.
However, the use of such a mandrel with grooves requires great precision when manufacturing the stringers and machining of the grooves of the mandrel.
In addition, it is in practice difficult to hold each stringer in position in its associated groove until the stringer is covered by a strip of prepreg.
The method thus proves complex, lengthy and expensive to implement.
Moreover, there is a need in mass reduction as regards aircraft fuselage skins.
There is also a need in space for accommodating utility systems.